1. Field of the Invention
The present invention relates to a linear actuator for both vibrating and rolling movement, capable of reciprocating in both a linear and a rolling manner, and an electric toothbrush using the same.
2. Description of the Related Art
A linear actuator capable of reciprocating linearly along a given axis and rolling about the axis has been disclosed in Japanese Patent Application Laid-open Publication No. 2004-343933. The linear actuator is composed of a shaft supported so as to reciprocate linearly along an axis thereof and to roll about the axis, a linear driver for causing the shaft to reciprocate linearly along the axis, and a linear driver for causing the shaft to roll about the axis.
The linear driver for linearly reciprocating movement is composed of a vibrating element and a stator. The vibrating element is cylinder-shaped and provided coaxially around a part of the circumference of the shaft. Also, the vibrating element is provided at both ends thereof with cylindrical permanent magnets having different magnetic poles on both ends thereof. The stator of the linear driver for linearly reciprocating movement is cylinder-shaped and arranged coaxially around the vibrating element. Also, this stator has a winding wire therearound.
The linear drive for rollingly reciprocating movement is composed of a rolling member and a stator. The rolling member is composed of a permanent magnet and a yoke and provided coaxially around another part of the shaft. The stator of the linear driver for rollingly reciprocating movement is cylinder-shaped and arranged coaxially around the rolling element. Also, this stator has a winding wire therearound.
In addition, the linear actuator according to the aforementioned publication is provided with a vibration absorbing weight independently from the above movable members in order to absorb unwanted vibration caused by linear reciprocation along the axis. Namely, such unwanted vibration is absorbed by vibrating the vibration absorbing weight in opposite phase to the moving components composed of the shaft and the movable members.
However, since vibration is absorbed by the vibration absorbing weight moving in opposite phase to the movable members, the vibration absorbing weight is indispensable in addition to the movable members, thereby making the electric toothbrush larger and heavier. In addition, due to an increase in size and total weight, more energy is required for causing reciprocating movements, thereby reducing a driving efficiency.